This is a proposal to develop a very high-resolution gamma ray Single Photon Emission Computed Tomography (SPECT) camera capable of imaging a wide variety of laboratory animals, from the brain of non-human primates to the whole body of a rat or mouse. The system also includes high-resolution x-ray Computed Tomography (CT) imaging capability of the same subject volume as the SPECT scanner. The imaging characteristics will surpass those of current clinical systems by employing an innovative gamma-ray detector system and collimator geometry that is designed specifically for this application. The camera developed here will meet a new and increasing demand for higher resolution, quantitative, and functional micro imaging in the laboratory setting. Applications include imaging of the central nervous system of non-human primates for the purposes of furthering our knowledge about the functional processes at the micro-level, developing diagnostic and therapeutic pharmaceuticals, and imaging of other animals for the development of cancer seeking radiopharmaceuticals for both diagnostic and therapeutic purposes. Semiconductor radiation detectors have evolved to the extent that we are now able to replace existing technology with solid-state technology that provides both improved performance and more compact designs. The system will consist of over 9000 16 mm solid-state detector pixels with mean energy resolution of 58% IFWHM at 140 keV This represents improvements in intrinsic spatial resolution and energy resolution of a factor of two compared with conventional gamma cameras. The prototype scanner will be capable of non-invasive, internal, in vivo, quantitative functional and fully 3-dimensional imaging of animals from mice to non-human primate brains.